An optical waveguide is meant to guides electromagnetic waves in the optical spectrum. Optical waveguides notably include optical fibers and rectangular waveguides. They are used as components in integrated optical circuits or as transmission medium in optical communication systems. Such waveguides are usually classified according to their geometry, mode structure, refractive index distribution and material. Of particular interest are the flexible optical waveguide ribbons.
A number of prior art documents relate to this background. For example:                U.S. Pat. No. 5,281,305 B1 discloses a method for producing stacked optical waveguides in a silicon dioxide substrate.        U.S. Pat. No. 5,937,128 B1 is directed to a waveguide connector and a method of forming a waveguide connector;        U.S. Pat. No. 6,317,964 B1 discloses a waveguide connector and a method and arrangement for aligning the waveguide connector to at least one optical device.        U.S. Pat. No. 6,496,624 B1 relates to an optical waveguide device for optical wiring and manufacturing. Here, a polymeric waveguide comprises a film-shaped optical waveguide.        U.S. Pat. No. 6,695,488 B2 discloses a tool and a method for forming a multi fiber ferrule. The multi fiber optical ferrule is formed of two ferrule halves.        U.S. Pat. No. 6,990,263 B2 discloses a connector-integrated type polymer optical waveguide and a method and a mold for producing the same.        U.S. Pat. No. 7,295,743 B2 discloses an optical waveguide, an optical waveguide ferrule and an optical connector.        U.S. Pat. No. 7,397,995 B, is directed to a multiple-core planar optical waveguide is disclosed. Overlapping portions of the waveguide cores are positioned one above the other and substantially parallel.        U.S. Pat. No. 7,457,499, discloses a method and apparatus are described, which permit the manufacture of an end of an optical fiber bundle.        US 2006/0045444 A1, relates to fiber bundles and methods for making fiber bundles.        WO/02/48752 relates to a low-profile waveguide assembly for interfacing a two-dimensional optoelectronic array to standard fiber bundles.        WO/2005/079502 is directed to a connector, wherein two impacts mounted seven optical fiber ferrules are aligned through the alignment of the central optical fiber and the alignment of at least one of the outer optical fibers in the ferrules.        
Similarly, a vast literature (non-patent document) is directed to the general background. For example:                “An optical coupling technique for parallel optical interconnection modules using polymeric optical waveguide films”, Usui, M.; Hikita, M.; Yoshimura, R.; Matsuura, N.; Sato, N.; Ohki, A.; Kagawa, T.; Tateno, K.; Katsura, K.; Ando, Y., DOI: 10.1109/IEMTIM.1998.704538, directed to the development of a new optical coupling technique for Para BIT modules using polymeric optical waveguide films.        “Stacked polymeric multimode waveguide arrays for two-dimensional optical interconnects”, Joon-Sung Kim; Jang-Joo Kim, DOI: 10.1109/JLT.2004.824523, wherein 2-D polymeric multimode waveguide arrays with two reflection-mirrors have been fabricated for optical interconnects between 2-D arrayed vertical-cavity surface-emitting lasers and detectors.        “Super Low-Loss, Super High-Density Multi-Fiber Optical Connectors”, Katsuki Suematsu, Masao Shinoda, Takashi Shigenaga, Jun Yamakawa, Masayoshi Tsukamoto, Yoshimi Ono and Takayuki Ando, Furukawa Review, No. 23, 2003, pages 53 to 58, authors have developed super low-loss, super high-density connectors, and assembly technology based on innovative high-precision molding technology.        In the document entitled “Fabrication of microgrooves with excimer laser ablation techniques for plastic optical fiber array alignment purposes”, K Naessens, A Van Hove, T Coosemans, S Verstuyft, Proc. SPIE, Vol. 3933, 309 (2000); DOI:10.1117/12.387568, authors present laser ablation as a fabrication method for micro machining in of arrays consisting of precisely dimensioned U-grooves in dedicated polycarbonate and polymethylmetacrylate plates. The fabricated plates are used to hold optical fibers by means of a UV-curable adhesive. Stacking and gluing of the plates allows the assembly of a 2D connector of plastic optical fibers for short distance optical interconnects.        “Development of a new fabrication method for stacked optical waveguides using inorganic-organic copolymers”, Streppel, U., Dannberg, P., Wächter, C., Bräuer, A., Nicole, P., Fröhlich, L., Houbertz, R., Popall, M., Institute of Electrical and Electronics Engineers-IEEE-: Polytronic 2001, International Conference on Polymers and Adhesives in Microelectronics and Photonics. Proceedings. New York, N.Y.: IEEE, 2001, pp. 329-335, presents a technology for the stacking of optical waveguides using hybrid inorganic-organic polymers (ORMOCEROs).        “Fabrication of a 2D connector for coupling a 4×8 array of small diameter plastic optical fiber (117/125 μm) to RCLED or VCSEL arrays”, Coosemaus, T. Van Hove, A. Naessens, K. Vanwassenhove, L. Van Daele, P. Baets, R., Dept. of Inf. Technol., Ghent Univ., as appears in: Electronic Components and Technology Conference, 2000. DOI: 10.1109/ECTC.2000.853332, authors discuss 2D parallel fiber arrays and report on the fabrication of a prototype 2D-connector that can be replicated using standard molding techniques.        
This being said, it is still a challenge to provide a method or a tool for assembling flexible optical waveguide ribbons with controlled positioning. It is a further challenge to reliably and efficiently provide an assembled stack of such ribbons with tolerances in the positioning of a few micrometers (μm) only.